1. Field of the Invention
The present invention generally relates to the detection of organic and inorganic dissolved or gaseous substances in fluids, and, in particular, to the analysis of fluid flow systems for the characterization and quantification of organic and inorganic dissolved or gaseous substances therein. More particularly, this invention relates to devices and methods for measuring cumulative mass fluxes of organic and inorganic dissolved or gaseous substances and cumulative fluid fluxes in fluid flow systems. The term fluid as used herein encompasses any type of liquid or gaseous media (e.g. water or air) containing or not one or more organic and/or inorganic dissolved or gaseous substances (e.g. contaminants or nutrients), while the term flow systems as used herein includes, but is not limited to, constructed flow systems such as closed conduits (e.g. pipes, sewers, vents, stacks, or chimneys) or open conduits (e.g. aqueducts, canals, ditches, rivers, or streams), and natural flow systems (e.g. natural water bodies such as estuaries, lakes, wetlands, and oceans). The term target chemical as used herein encompass dissolved inorganic and organic chemicals and inorganic and organic gases present in the fluid and these target chemicals may include contaminants, pollutants, and nutrients. However, as opposed to our earlier issued U.S. Pat. No. 6,401,547, which describes an approach to determining cumulative fluid fluxes and cumulative target chemical mass fluxes through porous media (pressure potential flow), the herein presented invention aims at applications that complement the before mentioned patent to non-porous fluid flow systems (velocity potential flow).
2. Description of the Relevant Art
The presence and transport of target chemicals in fluid flow systems can present significant pollution problems to nature and society and can be of great importance to industrial processes. For example, as to surface water supplies or other water resources (short: water flow systems), a wide variety of organic and inorganic target chemicals may be present in this particular type of flow system depending on how contiguous lands drained by or feeding said flow systems have been used and if said fluid flow systems receive contaminated water derived from external sources (e.g., septic systems, drainage tiles, industrial and municipal outfalls etc.). Many different organic and inorganic compounds (e.g., non-halogenated and halogenated organic compounds) may exist in water flow systems adjacent to factory sites, agricultural lands, military bases, urban areas, and other locations where extensive use of these chemicals has occurred over long time periods or accidental spills or inappropriate disposal have occurred. Of particular concern are pesticides, endocrine disrupters, halogenated (e.g., chlorinated) solvents including perchloroethene (PCE), trichloroethene (TCE), dichloroethane (DCA), vinyl chloride (VC), methylene chloride (MC), and others. However, in addition to the above organic compounds, a wide variety of other organic compounds shall be encompassed within the term “organic contaminants” as discussed below. Of equal concern is the presence of benzene, toluene, xylenes, and other constituents of petroleum-based fuels (e.g., jet fuel, gasoline, diesel fuel, and the like) in waste-bearing geologic formations underlying various transportation-related facilities. Examples of such facilities include gasoline stations, airports, military bases, and the like. Other contaminants include various pesticides and inorganic/organic nutrients used in crop production or suburban lawns and gardens or golf courses; and trace metals such as arsenic and chromium and the like used in industrial operations. At many sites, both organic and inorganic contaminants may be found as mixtures. A contaminant group designated as polyaromatic hydrocarbons (PAHs), such as naphthalene, phenanthene, anthracene, benzo-a-pyrene and others, are constituents of coal and/or tars and creosote found at former gas manufacturing sites and wood treating facilities. Regardless of the particular target chemicals of concern, the presence of these chemicals in water flow systems, as illustrated in this example, is a considerable public health concern and of ecological significance. As this example furthermore demonstrates, the present invention shall not be restricted to the monitoring of any given organic or inorganic compounds.
In general, several methods have been used to analyze fluids (and in particular water) for dissolved compounds and to quantify flows (fluxes integrated over transect areas) in fluid flow systems. In fact, our earlier issued U.S. Pat. No. 6,401,547 describes an approach to determining cumulative liquid fluxes and cumulative target chemical mass fluxes through porous media. Other examples involving direct methods for measuring fluid discharges include: acoustic or electromagnetic methods, and methods based on direct measurements of local flow velocities (fluid fluxes), e.g., using current meters to measure local fluxes, in a stream for the purpose of calculating depth integrated stream discharges using some standard method (e.g. two-point method, integrated measurement method, etc.). More examples that are potentially related to water flow systems are: tracer dilution methods (sudden or constant injection), as well as methods based on the deployment of hydraulic devices (e.g. weirs or notches). Furthermore, water discharges can be measured indirectly through monitoring the stage of a stream and inferring the discharge from a known stage-discharge relationship. Descriptions of all these methods are widely available in hydrology literature.
Measurements of target chemical mass discharges are generally performed by taking fluid samples at discrete moments in time and at discrete locations over transects. The fluid samples are analyzed for concentrations of target chemicals and the resultant mass fluxes calculated as the product of the target chemical concentrations and the measured or estimated fluid fluxes (velocities). Often is the case that short-term concentrated sampling events are conducted to generate a time-series of measurements from some peak event (e.g. a storm or spill). Hundreds of fluid samples may be collected and processed for the purpose of estimating related cumulative mass loads of target chemicals (target chemical mass fluxes integrated over a transect area) transported in a fluid flow system. From the nature of most of the methods mentioned it can be observed that fluid discharges are only measured at discrete points in time and that cumulative or time averaged discharges have to be obtained from interpolating and integrating of recorded data time series. The same applies to the measurement of the mass discharges of target chemical, which, in addition, are only indirectly obtained from concentration and fluid flux data. Hence, the measurement of cumulative or time averaged fluid and target chemical mass discharges can be performed with current methods, yet the technical requirements in the field for data transmission and logging are considerable and for target chemical mass discharge additional computations are required to arrive at final flux estimates.
While the prior methods provide important information regarding the levels of contamination in fluid flow systems of concern, they do not allow direct measurements of target chemical mass fluxes. And although prior methods and apparatus are capable of measuring instantaneous fluid fluxes, most do not allow direct measurements of cumulative fluid fluxes. Finally, the commonly used methods that exist do not permit simultaneous measurements of target chemical cumulative mass fluxes and cumulative fluid fluxes.
Current methods for estimating the target-chemical mass flux (Jsol) in fluid flow systems are made from independent instantaneous point measurements of fluid flux (vo) and target chemical concentration (C) in sampled fluids. Several methods exist for measuring vo and C in fluid flow systems, and all provide measures at discrete moments in space and time. However, no single method exists for non-porous fluid flow systems that samples vo and C at coincident points in space and time and no method exists to measure cumulative target chemical mass flux and cumulative fluid flux. Measured vo and C are used as shown in the following equation to estimate the instantaneous target chemical mass flux, J.Jsol=voC   (1)Equation (1) is assumed to characterize target chemical mass flux at a point in space or over a specified sampling dimensions (i.e., an area perpendicular to the direction of fluid flow) and for a reported sampling time. For dynamic fluid flow systems, this approach of characterizing target chemical mass flux is subject to significant experimental and conceptual errors. Consider first, that the fluid flux, vo and the target chemical concentration, C are both functions of position and time. This suggests that the magnitude of the target chemical mass flux, Jsol, also varies with position and time. Thus, any sampling of vo and C that does not occur at coincident points in space and time precludes accurate local estimation of the magnitude of both fluid and target chemical mass fluxes. Second, the short-term sampling procedures often used to obtain C and vo preclude estimation of the time-integrated (i.e., cumulative) values for fluid flux and target chemical mass flux. Such time-integrated target chemical mass fluxes are useful for assessing health risks associated with contamination found in water or air flow systems, for example, such as for assessing contaminant loads generated within watersheds or along stream and river reaches, for assessing the total amount of off-site contamination contributed by one or more sources, and for assessing the benefits of removing or remediating sources of contamination. Moreover, the inherent time integration of both fluid flux and especially target chemical mass flux at sampling points performed by the invention allow for the quantification of target chemical mass loads that can not be measured by traditional concentration sampling any more if the target chemical concentrations are below the detection limit of the applied technology. However, target chemical mass loads may still be considerable, even for very high degrees of dilution if the fluid discharge is high enough. In addition, the time integration of measured fluid flux and target chemical mass flux eliminates the risk of not detecting some peak event (e.g. storm or spill) as it may be the case with time-discrete flux and concentration sampling.
Traditional testing methods also require a large amount of expensive equipment, are labor intensive, and involve complex operating procedures. Moreover, conventional monitoring techniques which require the removal of numerous fluid samples for individual testing typically generate large quantities of waste products (e.g., residual sample materials) that, if sufficiently contaminated or hazardous by their nature, can present significant disposal problems. Prior to the development of the present invention, a need therefore remained for an efficient testing system which avoids these disadvantages and enables fluid flow systems to be tested in an accurate, rapid, and effective manner.
The claimed invention represents a unique and highly-efficient alternative to the methods listed above. It does not require extensive equipment (e.g., pumps) and complex operating procedures. The invented device can be used to analyze large fluid flow systems without extracting any contaminated fluid sample materials so that problems with disposal of generated waste fluids are avoided. The invented device can be used to obtain cumulative estimates of the magnitude of both fluid and target chemical mass fluxes at specified point locations over the two dimensions of a transect that is oriented perpendicular to the direction of flow in the flow system. Alternatively, it can be used to provide instantaneous analysis of the flow system through the use of electronic pressure transducers and chemical sensors. The instantaneous information can be obtained alone or in combination with the cumulative analysis. Finally, the method and apparatus described below enable the fluid flow system of interest to be analyzed at multiple locations simultaneously so that target chemical mass loadings to the flow system may be “mapped” and thus, enabling, for example, the delineation of locations of concern such as target chemical sources (e.g. certain watershed areas, stream segments, water bodies etc.). Decontamination of water flow systems, for example, can then occur in a more site-specific and accurate manner. The present invention therefore involves a highly effective testing system which represents a substantial advance in the art of target chemical (e.g., nutrient or contaminant) detection, target chemical source delineation, and remediation of, in particular, water flow systems as discussed further below.
However, according to the initial definition of the term “fluid” as used herein, the potential applications of the invention shall not be restricted by any means to the example given above, which uses water as a fluid in order to be most illustrative. Other examples for potential applications include point source identification of air pollution (e.g. industrial plants), quality control of fluids required in industrial processes (e.g. purity or chemical composition of liquids).